Improving dietary intake of Dutch adults is important in order to prevent overweight and related health risks. Food choices are made both consciously and less consciously. As a result, supporting healthy food choices can be done in various ways, including by making changes to the physical food environment. The worksite cafeteria is such a food environment. The aim of this thesis is to develop the intervention The healthy worksite cafeteria with nudging and social marketing strategies and to evaluate its effectiveness on objectively measured purchase behaviour of Dutch employees in the worksite cafeteria.